Type 2 MI and Myocardial Injury in the Era of High-sensitivity Troponin

Abstract

Troponin has been the cornerstone of the definition of MI since its introduction to clinical practice. High-sensitivity troponin has allowed clinicians to detect degrees of myocardial damage at orders of magnitude smaller than previously and is challenging the definitions of MI, with implications for patient management and prognosis. Detection and diagnosis are no doubt enhanced by the greater sensitivity afforded by these markers, but perhaps at the expense of specificity and clarity. This review focuses on the definitions, pathophysiology, prognosis, prevention and management of type 2 MI and myocardial injury. The five types of MI were first defined in 2007 and were recently updated in 2018 in the fourth universal definition of MI. The authors explore how this pathophysiological classification is used in clinical practice, and discuss some of the unanswered questions in this era of availability of high-sensitivity troponin.

Keywords: Type 2 MI; high-sensitivity troponin; myocardial injury.

Figure 1:. Classification of MI and Myocardial Injury as per the Fourth Universal Definition of MI

Figure 2:. Determinants of Oxygen Supply–Demand Mismatch Leading to Type 2 MI

Figure 3:. Cardiomyocyte Molecular Signalling Pathways Triggered by Ischaemia

Figure 4:. Limits of Detection of Past and Current Troponin I Assays

Figure 5:. Molecular Composition of Troponin Complexes, and Mechanisms of Release into the Bloodstream